/*    Copyright 2013 10gen Inc.
 *
 *    This program is free software: you can redistribute it and/or  modify
 *    it under the terms of the GNU Affero General Public License, version 3,
 *    as published by the Free Software Foundation.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU Affero General Public License for more details.
 *
 *    You should have received a copy of the GNU Affero General Public License
 *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 *    As a special exception, the copyright holders give permission to link the
 *    code of portions of this program with the OpenSSL library under certain
 *    conditions as described in each individual source file and distribute
 *    linked combinations including the program with the OpenSSL library. You
 *    must comply with the GNU Affero General Public License in all respects
 *    for all of the code used other than as permitted herein. If you modify
 *    file(s) with this exception, you may extend this exception to your
 *    version of the file(s), but you are not obligated to do so. If you do not
 *    wish to do so, delete this exception statement from your version. If you
 *    delete this exception statement from all source files in the program,
 *    then also delete it in the license file.
 */

#include "mongo/platform/basic.h"

#include "mongo/logger/rotatable_file_writer.h"

#include <boost/filesystem/operations.hpp>
#include <boost/scoped_array.hpp>
#include <cstdio>
#include <fstream>

#include "mongo/base/string_data.h"
#include "mongo/util/mongoutils/str.h"

namespace mongo {
namespace logger {

namespace {
    /**
     * Renames file "oldName" to "newName".
     *
     * Both names are UTF-8 encoded.
     */
    int renameFile(const std::string& oldName, const std::string& newName);
}  // namespace

#ifdef _WIN32
namespace {

    /**
     * Converts UTF-8 encoded "utf8Str" to std::wstring.
     */
    std::wstring utf8ToWide(const StringData& utf8Str) {
        if (utf8Str.empty())
            return std::wstring();

        // A Windows wchar_t encoding of a unicode codepoint never takes more instances of wchar_t
        // than the UTF-8 encoding takes instances of char.
        boost::scoped_array<wchar_t> tempBuffer(new wchar_t[utf8Str.size()]);
        tempBuffer[0] = L'\0';
        int finalSize = MultiByteToWideChar(
                CP_UTF8,               // Code page
                0,                     // Flags
                utf8Str.rawData(),     // Input string
                utf8Str.size(),        // Count
                tempBuffer.get(),      // UTF-16 output buffer
                utf8Str.size()         // Buffer size in wide characters
        );
        // TODO(schwerin): fassert finalSize > 0?
        return std::wstring(tempBuffer.get(), finalSize);
    }


    /**
     * Minimal implementation of a std::streambuf for writing to Win32 files via HANDLEs.
     *
     * We require this implementation and the std::ostream subclass below to handle the following:
     * (1) Opening files for shared-delete access, so that open file handles may be renamed.
     * (2) Opening files with non-ASCII characters in their names.
     */
    class Win32FileStreambuf : public std::streambuf {
        MONGO_DISALLOW_COPYING(Win32FileStreambuf);
    public:
        Win32FileStreambuf();
        virtual ~Win32FileStreambuf();

        bool open(const StringData& fileName, bool append);
        bool is_open() { return _fileHandle != INVALID_HANDLE_VALUE; }

    private:
        virtual std::streamsize xsputn(const char* s, std::streamsize count);
        virtual int_type overflow(int_type ch = traits_type::eof());

        std::streamsize writeToFile(const char* s, std::streamsize count);

        HANDLE _fileHandle;
    };

    /**
     * Minimal implementation of a stream to Win32 files.
     */
    class Win32FileOStream : public std::ostream {
        MONGO_DISALLOW_COPYING(Win32FileOStream);
    public:
        /**
         * Constructs an instance, opening "fileName" in append or truncate mode according to
         * "append".
         */
        Win32FileOStream(const std::string& fileName, bool append) : std::ostream(&_buf), _buf() {

            if (!_buf.open(fileName, append)) {
                setstate(failbit);
            }
        }

        virtual ~Win32FileOStream() {}

    private:
        Win32FileStreambuf _buf;
    };

    Win32FileStreambuf::Win32FileStreambuf() : _fileHandle(INVALID_HANDLE_VALUE) {}
    Win32FileStreambuf::~Win32FileStreambuf() {
        if (is_open()) {
            CloseHandle(_fileHandle);  // TODO(schwerin): Should we check for failure?
        }
    }

    bool Win32FileStreambuf::open(const StringData& fileName, bool append) {
        _fileHandle = CreateFileW(
                utf8ToWide(fileName).c_str(),         // lpFileName
                GENERIC_WRITE,                        // dwDesiredAccess
                FILE_SHARE_DELETE | FILE_SHARE_READ,  // dwShareMode
                NULL,                                 // lpSecurityAttributes
                OPEN_ALWAYS,                          // dwCreationDisposition
                FILE_ATTRIBUTE_NORMAL,                // dwFlagsAndAttributes
                NULL                                  // hTemplateFile
                );


        if (INVALID_HANDLE_VALUE == _fileHandle)
            return false;

        LARGE_INTEGER zero;
        zero.QuadPart = 0LL;

        if (append) {
            if (SetFilePointerEx(_fileHandle, zero, NULL, FILE_END)) {
                return true;
            }
        }
        else {
            if (SetFilePointerEx(_fileHandle, zero, NULL, FILE_BEGIN) &&
                SetEndOfFile(_fileHandle)) {

                return true;
            }

        }
        // TODO(schwerin): Record error info?
        CloseHandle(_fileHandle);
        return false;
    }

    std::streamsize Win32FileStreambuf::writeToFile(const char* s, std::streamsize count) {
        DWORD totalBytesWritten = 0;

        while (count > totalBytesWritten) {
            DWORD bytesWritten;
            if (!WriteFile(
                        _fileHandle,
                        s,
                        count - totalBytesWritten,
                        &bytesWritten,
                        NULL)) {
                break;
            }
            totalBytesWritten += bytesWritten;
        }

        return totalBytesWritten;
    }

    // Called when strings are written to ostream
    std::streamsize Win32FileStreambuf::xsputn(const char* s, std::streamsize count) {
        DWORD totalBytesWritten = 0;

        // Scan for embedded newlines before end
        // this should be rare since the newline should only be at the end
        const char* startPos = s;
        for (int i = 0; i < count; i++) {
            if (s[i] == '\n') {
                totalBytesWritten += writeToFile(startPos, i - (startPos - s));
                writeToFile("\r\n", 2);
                totalBytesWritten += 1; // Caller expected we only wrote 1 char, so tell them so
                startPos = &s[i + 1];
            }
        }

        // Did the string not end on "\n"? Write the remaining, no need for CRLF
        // as upper layers are responsible for it
        if ((startPos - s) != count) {
            totalBytesWritten += writeToFile(startPos, count - (startPos - s));
        }

        return totalBytesWritten;
    }

    // Overflow is called for single character writes to the ostream
    Win32FileStreambuf::int_type Win32FileStreambuf::overflow(int_type ch) {
        if (ch == traits_type::eof())
            return ~ch;  // Returning traits_type::eof() => failure, anything else => success.
        char toPut = static_cast<char>(ch);
        if (1 == xsputn(&toPut, 1))
            return ch;
        return traits_type::eof();
    }

    // Win32 implementation of renameFile that handles non-ascii file names.
    int renameFile(const std::string& oldName, const std::string& newName) {
        return _wrename(utf8ToWide(oldName).c_str(), utf8ToWide(newName).c_str());
    }

}  // namespace
#else

namespace {

    // *nix implementation of renameFile that assumes the OS is encoding file names in UTF-8.
    int renameFile(const std::string& oldName, const std::string& newName) {
        return rename(oldName.c_str(), newName.c_str());
    }

}  // namespace
#endif

    RotatableFileWriter::RotatableFileWriter() : _stream(NULL) {}

    RotatableFileWriter::Use::Use(RotatableFileWriter* writer) :
        _writer(writer),
        _lock(writer->_mutex) {
    }

    Status RotatableFileWriter::Use::setFileName(const std::string& name, bool append) {
        _writer->_fileName = name;
        return _openFileStream(append);
    }

    Status RotatableFileWriter::Use::rotate(bool renameOnRotate, const std::string& renameTarget) {
        if (_writer->_stream) {
            _writer->_stream->flush();

            if(renameOnRotate) {
                try {
                    if (boost::filesystem::exists(renameTarget)) {
                        return Status(ErrorCodes::FileRenameFailed, mongoutils::str::stream() <<
                                      "Renaming file " << _writer->_fileName << " to " <<
                                      renameTarget << " failed; destination already exists");
                    }
                } catch (const std::exception& e) {
                        return Status(ErrorCodes::FileRenameFailed, mongoutils::str::stream() <<
                                      "Renaming file " << _writer->_fileName << " to " <<
                                      renameTarget << " failed; Cannot verify whether destination "
                                      "already exists: " << e.what());
                }

                if (0 != renameFile(_writer->_fileName, renameTarget)) {
                    return Status(ErrorCodes::FileRenameFailed, mongoutils::str::stream() <<
                                  "Failed  to rename \"" << _writer->_fileName << "\" to \"" <<
                                  renameTarget << "\": " << strerror(errno) << " (" << errno << ')');
                    //TODO(schwerin): Make errnoWithDescription() available in the logger library, and
                    //use it here.
                }
            }
        }
        return _openFileStream(false);
    }

    Status RotatableFileWriter::Use::status() {
        if (!_writer->_stream) {
            return Status(ErrorCodes::FileNotOpen,
                          mongoutils::str::stream() << "File \"" << _writer->_fileName <<
                          "\" not open");
        }
        if (_writer->_stream->fail()) {
            return Status(ErrorCodes::FileStreamFailed,
                          mongoutils::str::stream() << "File \"" << _writer->_fileName <<
                          "\" in failed state");
        }
        return Status::OK();
    }

    Status RotatableFileWriter::Use::_openFileStream(bool append) {
        using std::swap;

#ifdef _WIN32
        boost::scoped_ptr<std::ostream> newStream(
                new Win32FileOStream(_writer->_fileName, append));
#else
        std::ios::openmode mode = std::ios::out;
        if (append) {
            mode |= std::ios::app;
        }
        else {
            mode |= std::ios::trunc;
        }
        boost::scoped_ptr<std::ostream> newStream(
                new std::ofstream(_writer->_fileName.c_str(), mode));
#endif

        if (newStream->fail()) {
            return Status(ErrorCodes::FileNotOpen, "Failed to open \"" + _writer->_fileName + "\"");
        }
        swap(_writer->_stream, newStream);
        return status();
    }

}  // namespace logger
}  // namespace mongo
